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Презентация на тему Volcanoes: Eruptions and Hazards

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What is a volcano? A volcano is a vent or 'chimney' that connects molten rock (magma) from within the Earth’s crust to the Earth's surface. The volcano includes the surrounding cone of erupted material. ventconemagma chamberconduit
Volcanoes: Eruptions and Hazards What is a volcano? A volcano is a vent or 'chimney' that What causes volcanoes?The Formation of Magma Mantle rock melts when the temperature What causes volcanoes?Where Volcanoes Form Tectonic Plate Boundaries!!!~75% world’s active volcanoes in Ring of Fire PlatesEarthquakesVolcanoesVolcanoes and Earthquakes are found on places where plates meet What causes volcanoes? What causes volcanoes?Hot Spots How and why do volcanoes erupt?Hot, molten rock (magma) is buoyant (has Large amounts of gas and a high viscosity (sticky) magma will form The Composition of Magma Determines whether it is explosive or not!High Pyroclastic material Rock fragments created by 		   eruptionsmagma explodes What Erupts from a Volcano?Lava can be 	thick or thin.Blocky lavaPahoehoeAaPillow lava How do volcanoes affect the Earth?Flows and Fallouts hot ash can flow Types of VolcanoesShield volcanoCinder cone volcanoComposite volcano Craters, Calderas, and Lava PlateauCrater From explosions of material out of the Explosive EruptionsMt. RedoubtExplosive volcanic eruptions can be catastrophicErupt 10’s-1000’s km3 of magmaSend Three products from an explosive eruptionAsh fallPyroclastic flowPyroclastic surgeExplosive EruptionsPyroclastic flows on Direct measurements of pyroclastic flows are extremely dangerous!!! Effusive EruptionsEffusive eruptions are characterised by outpourings of lava on to the ground.HawaiiCourtesy of www.swisseduc.ch Pyroclastic flowLahars/Mud flowsPyroclastic fallLava flowNoxious GasEarthquakesVolcanic HazardsCourtesy of www.swisseduc.ch Pyroclastic FlowFor example, eruption of Vesuvius in 79 AD destroyed the city of Pompeii Pompeii (79AD)	On August 24, 79AD Mount Vesuvius literally blew its top, erupting Pompeii (79AD)	Pyroclastic flows of poisonous gas and hot volcanic debris engulfed the Pompeii (79AD)	The cities remained buried and undiscovered for almost 1700 years until How do pyroclastic flows cause devastation? Pyroclastic Flow - laharsHot volcanic activity can melt snow and iceMelt water Pyroclastic FallAsh loadCollapses roofsBrings down power linesKills plantsContaminates water suppliesRespiratory hazard for humans and animals Lava FlowIt is not just explosive volcanic activity that can be hazardous. Volcano MonitoringVolcano Observatories are set up on all active volcanoes that threaten SeismicityDeformationGas Output (on volcano and remote sensing techniques)These three things are the Gas samples are collected from fumaroles and active vents. Gas levels In Summary..Volcanoes are extremely hazardous. However, the volcano can be studied, monitored
Слайды презентации

Слайд 2 What is a volcano?
A volcano is a

What is a volcano? A volcano is a vent or 'chimney'

vent or 'chimney' that connects molten rock (magma) from

within the Earth’s crust to the Earth's surface.
The volcano includes the surrounding cone of erupted material.

vent

cone

magma chamber

conduit


Слайд 3 What causes volcanoes?
The Formation of Magma
Mantle rock

What causes volcanoes?The Formation of Magma Mantle rock melts when the

melts when the temperature increases
or the pressure decreases.


Слайд 4 What causes volcanoes?
Where Volcanoes Form
Tectonic Plate Boundaries!!!

~75%

What causes volcanoes?Where Volcanoes Form Tectonic Plate Boundaries!!!~75% world’s active volcanoes in Ring of Fire

world’s active volcanoes in Ring of Fire


Слайд 5 Plates
Earthquakes
Volcanoes
Volcanoes and Earthquakes are found on places where

PlatesEarthquakesVolcanoesVolcanoes and Earthquakes are found on places where plates meet

plates meet


Слайд 6
What causes volcanoes?

What causes volcanoes?

Слайд 7
What causes volcanoes?
Hot Spots

What causes volcanoes?Hot Spots

Слайд 8 How and why do volcanoes erupt?
Hot, molten rock

How and why do volcanoes erupt?Hot, molten rock (magma) is buoyant

(magma) is buoyant (has a lower density than the

surrounding rocks) and will rise up through the crust to erupt on the surface.
Same principle as hot air rising, e.g. how a hot air balloon works
When magma reaches the surface it depends on how easily it flows (viscosity) and the amount of gas (H2O, CO2, S) it has in it as to how it erupts.

Слайд 9 Large amounts of gas and a high viscosity

Large amounts of gas and a high viscosity (sticky) magma will

(sticky) magma will form an explosive eruption!
Think about shaking

a carbonated drink and then releasing the cap.
Small amounts of gas and (or) low viscosity (runny) magma will form an effusive eruption
Where the magma just trickles out of the volcano (lava flow).

How and why do volcanoes erupt?


Слайд 10 The Composition of Magma Determines whether it is

The Composition of Magma Determines whether it is explosive or not!High

explosive or not!
High

content
More likely to be !!!
High content
More likely to be !!!
Why?
Silica has a thick, stiff consistency
Flows slowly
Tends to Harden in the volcano’s vent

water

silica

EXPLOSIVE

EXPLOSIVE


Слайд 11 Pyroclastic material
Rock fragments created by

Pyroclastic material Rock fragments created by 		  eruptionsmagma explodes

eruptions
magma explodes from volcano and solidifies in

the air
existing rock is shattered by powerful eruptions

Volcanic blocks

Volcanic bombs

Lapilli

Volcanic ash

EXPLOSIVE

What Erupts from a Volcano?


Слайд 12 What Erupts from a Volcano?
Lava can be
thick

What Erupts from a Volcano?Lava can be 	thick or thin.Blocky lavaPahoehoeAaPillow lava

or thin.
Blocky lava
Pahoehoe
Aa
Pillow lava


Слайд 13 How do volcanoes affect the Earth?
Flows and Fallouts

How do volcanoes affect the Earth?Flows and Fallouts hot ash can

hot ash can flow really quickly
Knock down buildings
Dam rivers

(flooding/drought)
Kill crops and livestock

Climatic Changes
Ash & Gases can block sunlight
Drop average global temperature noticeably


Слайд 14 Types of Volcanoes
Shield volcano
Cinder cone volcano
Composite volcano

Types of VolcanoesShield volcanoCinder cone volcanoComposite volcano

Слайд 15 Craters, Calderas, and Lava Plateau
Crater
From explosions of

Craters, Calderas, and Lava PlateauCrater From explosions of material out of

material out of the vent and the collapse of

material back into vent


Caldera
Much larger depression that forms when magma chamber empties and its roof collapses

Lava Plateau
Forms when lava erupts from long cracks, or fissures, and spreads out evenly (thousands of km)


Слайд 16 Explosive Eruptions
Mt. Redoubt
Explosive volcanic eruptions can be catastrophic
Erupt

Explosive EruptionsMt. RedoubtExplosive volcanic eruptions can be catastrophicErupt 10’s-1000’s km3 of

10’s-1000’s km3 of magma
Send ash clouds >25 km into

the stratosphere
Have severe environmental and climatic effects
Hazardous!!!

Above: Large eruption column and ash cloud from an explosive eruption at Mt Redoubt, Alaska


Слайд 17 Three products from an explosive eruption
Ash fall
Pyroclastic flow
Pyroclastic

Three products from an explosive eruptionAsh fallPyroclastic flowPyroclastic surgeExplosive EruptionsPyroclastic flows

surge
Explosive Eruptions
Pyroclastic flows on Montserrat, buried the capital city.


Слайд 18 Direct measurements of pyroclastic flows are extremely dangerous!!!

Direct measurements of pyroclastic flows are extremely dangerous!!!

Слайд 19 Effusive Eruptions
Effusive eruptions are characterised by outpourings of

Effusive EruptionsEffusive eruptions are characterised by outpourings of lava on to the ground.HawaiiCourtesy of www.swisseduc.ch

lava on to the ground.
Hawaii
Courtesy of www.swisseduc.ch


Слайд 20 Pyroclastic flow
Lahars/Mud flows
Pyroclastic fall
Lava flow
Noxious Gas
Earthquakes
Volcanic Hazards
Courtesy of

Pyroclastic flowLahars/Mud flowsPyroclastic fallLava flowNoxious GasEarthquakesVolcanic HazardsCourtesy of www.swisseduc.ch

www.swisseduc.ch


Слайд 21 Pyroclastic Flow
For example, eruption of Vesuvius in 79

Pyroclastic FlowFor example, eruption of Vesuvius in 79 AD destroyed the city of Pompeii

AD destroyed the city of Pompeii


Слайд 22 Pompeii (79AD)
On August 24, 79AD Mount Vesuvius literally

Pompeii (79AD)	On August 24, 79AD Mount Vesuvius literally blew its top,

blew its top, erupting tonnes of molten ash, pumice

and sulfuric gas miles into the atmosphere. Pyroclastic flows flowed over the city of Pompeii and surrounding areas.

Слайд 23 Pompeii (79AD)
Pyroclastic flows of poisonous gas and hot

Pompeii (79AD)	Pyroclastic flows of poisonous gas and hot volcanic debris engulfed

volcanic debris engulfed the cities of Pompeii, Herculaneum and

Stabiae suffocating the inhabitants and burying the buildings.

Слайд 24 Pompeii (79AD)
The cities remained buried and undiscovered for

Pompeii (79AD)	The cities remained buried and undiscovered for almost 1700 years

almost 1700 years until excavation began in 1748. These

excavations continue today and provide insight into life during the Roman Empire.

Слайд 25 How do pyroclastic flows cause devastation?

How do pyroclastic flows cause devastation?

Слайд 26 Pyroclastic Flow - lahars
Hot volcanic activity can melt

Pyroclastic Flow - laharsHot volcanic activity can melt snow and iceMelt

snow and ice
Melt water picks up rock and debris
Forms

fast flowing, high energy torrents
Destroys all in its path

Слайд 27 Pyroclastic Fall
Ash load
Collapses roofs
Brings down power lines
Kills plants
Contaminates

Pyroclastic FallAsh loadCollapses roofsBrings down power linesKills plantsContaminates water suppliesRespiratory hazard for humans and animals

water supplies
Respiratory hazard for humans and animals


Слайд 28 Lava Flow
It is not just explosive volcanic activity

Lava FlowIt is not just explosive volcanic activity that can be

that can be hazardous. Effusive (lava) activity is also

dangerous.

Слайд 29 Volcano Monitoring
Volcano Observatories are set up on all

Volcano MonitoringVolcano Observatories are set up on all active volcanoes that

active volcanoes that threaten the human population. These are

designed to monitor and potentially to predict the eruptive behaviour of the volcano in question.

Слайд 30 Seismicity
Deformation
Gas Output
(on volcano and remote sensing techniques)


These

SeismicityDeformationGas Output (on volcano and remote sensing techniques)These three things are

three things are the most important precursors to an

eruption.




Volcano Monitoring


Слайд 31 Gas samples are collected from fumaroles and

Gas samples are collected from fumaroles and active vents. Gas

active vents.




Gas levels may also be monitored

by remote sensing techniques

Gas Monitoring


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